Question

I am trying to build a basic REST client in PHP as a way to make myself familiar with the concept of dependency injection container. Ultimately, I would like to do something like:

$client = new RestClient();
$client->getService('user', array('id, optional fields...'));

But I also want to be able to specify which object should handle the request (if I want to use fopen instead of curl, for instance).

According to what I’ve read so far, a proper way to achieve this would be:

$request = new ServiceDefinition( 
    'Curl', 
    array('...') 
); 
$user = new ServiceDefinition('User',  
    array(new ServiceReference('request')) 
); 
$container = new ServiceContainer(array( 
    'request' => $request, 
    'user'    => $user, 
));

My question is: is there a simpler way to build the dependency between the user object and the request object ? (a basic setter injection on RestClient(), maybe ?)

Thanks in advance.

Answer 1

Depending on your existing familiarity with Dependency Injection, using a DI container may be jumping in at the deep end. In short, it’s certainly possible to substitute the container with simple setter injection:

interface HttpAdapterInterface {}
class CurlAdapter implements HttpAdapterInterface {}
class SocketAdapter implements HttpAdapterInterface {}

class RestClient {
    public function setHttpAdapter(HttpAdapterInterface $adapter) {
        // ...
    }
}

Fabien Potencier has a good series on DI, the second part of which covers DI containers (and when to use them).